Record Details

Ring Oscillator Based Temperature Sensor

Electronic Theses of Indian Institute of Science

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Field Value
 
Title Ring Oscillator Based Temperature Sensor
 
Creator Walvekar, Trupti
 
Subject Temperature Sensors
Temperature Sensor Design
Ring Oscillators
Complementary Metal Oxide Semiconductor Ring Oscillators
Ring Oscillator Temperature Sensors
Power Outlet Temperature Monitoring
Ring Oscillator Design
CMOS Ring Oscillator
Sensor Design
Electronic Engineering
 
Description The temperature sensor design discussed in this thesis, is meant mainly to monitor temperature at power outlets. Current variations in power cords have a direct impact on the surrounding temperature. Sensing these variations ,enables us to take necessary measures to prevent any hazards due to temperature rise. Thus, for this application we require a sensor with a moderate temperature error (_10C) over a sensing range of -200C to 1500C. Low power consumption and simple digitizing scheme alleviate measurement errors due to self heating effects of the sensor.
A current starved inverter based ring oscillator was chosen for the sensor design in 130nm technology. The inverter delay variation with temperature is used for sensing. Linearity and process invariancy of these characteristics are fundamental to the sensor design. We observed through simulations, and confirmed by mathematical analysis, that the sensing characteristics are governed by bias current dependence on temperature. Control voltage for the bias circuitry of the oscillator determines current through the inverter stages. Hence, for linear sensing characteristics, a control voltage(Vc) just above the maximum threshold voltage of bias transistor is used. This enables generation of PTAT saturation current for current starved inverters, due to dominance of threshold voltage decrease with temperature over mobility decrease.
I.Another limitation, process dependency of the sensing characteristics, was overcome through the proposed calibration based compensation technique. A changing Vc proportional to threshold voltage variation with process, process independent bias current and current temperature characteristics were obtained. This compensated for the process variation effects on frequency. Thus, a variable Vc was generated using a reference with low temperature sensitivity of 17.6_V=0C, and resistive divider combinations for various processes. Incorporating this compensation technique we achieved good linearity in sensor characteristics and a maximum temperature error of± 1.60C over the sensing range. The sensor consumes a low power of 0.29mW and also occupies minimal area.
 
Contributor Jamadagni, H S
 
Date 2016-06-20T07:20:08Z
2016-06-20T07:20:08Z
2016-06-20
2012-07
 
Type Thesis
 
Identifier http://etd.iisc.ernet.in/handle/2005/2541
http://etd.ncsi.iisc.ernet.in/abstracts/3296/G25613-Abs.pdf
 
Language en_US
 
Relation G25613